I'm going to add a SCSI2SD to a M5010 SE ( that's the one without the HD and the two floppy drives). So the only noisy thing in there apart from the FDDs is the fan, which is QUITE LOUD.
This SE was manufactured in 1987, making it one of the very early ones. It originally had the squirrel cage fan, but apparently this one was removed and replaced by a more common axial one when the Mac was serviced on the 8th of August 1991 (the guy left a sticker on the bottom).
So it's not original a